As arthritis deteriorates the pain can become debilitating and then surgery is considered. In some types of arthritis of the knee, only part of the joint is affected. This may be the inner half (most commonly), the outer half or under the knee cap. In this situation it is possible to replace the damaged part of the knee without resorting to a total knee replacement (TKR). This is called a unicompartmental knee replacement (UKR). This preserves all the knees ligaments and thus mimics the normal feeling and function of the natural knee as closely as possible.
The surgery involves removing a small thickness of damaged bone from the inside part of the knee. Less bone is removed than in a Total Knee Replacement and only from one side of the knee. The Unicompartmental Knee Replacement fits inside this prepared space. The Operation takes about an hour and involves a smaller surgical incision and a faster recovery. This is often described as ‘mini-invasive surgery’. This small incision does not involve cutting any muscle or tendons (as with a Total Knee Replacement), thus enabling quicker recovery from surgery.
The UKR comes in three parts. The femoral component is made of metal, is curved and highly polished. The tibial component is also metal. A plastic component, which is curved on the top and flat on the underside, fits into the tibial surface recreating the joint. This type of UKR is a so called 'fixed bearing' which avoids the potential risks of excessive wear of the plastic and plastic dislocation.
After a Unicompartmental Knee Replacement
The day after the operation your exercise regime begins. With the aid of a physiotherapist you will get out of bed and begin to exercise your new knee replacement. With perseverance, you should be able to climb stairs by day 2 or 3 and go home. You will need to continue attending physiotherapy as an outpatient. This can be done closer to your home with one of our recommended group of physiotherapists. For most people it will take a month or so to be walking reasonably. After three months you should be able to walk well without pain, climb stairs (leading with your operated leg) and be capable of a range of movement with your new knee from 0 degrees to at least 120 degrees.
It is important to remember that a unicompartmental knee replacement will not give you a normal knee, however, it will give excellent pain relief, very good function and range of movement, which will be better than a TKR. Biomechanical studies suggest a UKR allows the most normal knee function of any type of joint replacement. You will be able to walk a good distance and play recreational sports such tennis, golf, cycle or swim. We would not recommend running after a UKR.
Lifespan of a UKR
Studies suggest that a UKR has a better than 90% chance of surviving for more than 10 years. The small amount of bone removed means that it is relatively easy to revise it to a Total knee replacement if the UKR wears out. Revising a worn TKR is a much more complex procedure. UKR is therefore arguabley a good option for younger more active patients.